1. Field of the Invention
The present invention relates to a projection optical system, a projector, and an image reading device.
2. Description of the Related Art
A projection optical system for projectors is used in order to enlarge an image on a transmission or reflection type liquid crystal panel, a digital mirror device or the like, and project the enlarged image onto projection surfaces. A variety of projection optical systems are well-known at present.
Such a projection optical system is required to assure long back-focus, excellent telecentric performance at an incident side of light flux for forming enlarged images, efficiently corrected chromatic aberration and distortion, high MTF characteristics, and high resolution.
Projectors are strongly required to display large projection images, and to be compact. As one of such compact projectors, a rear projector has been proposed in Japanese Patent Laid-open Publication No. 2006-235516. The rear projector includes a projection optical system in which a lens system and one concave mirror are used in combination.